點進去它有詳細說明https://ifans.pixnet.net/blog/post/210117886-ca%EF%BC%9F3ca%EF%BC%9F%E6%83%B3%E7%9F%A5%E9%81%93%E4%BD%A0%E7%9A%84%E6%89%8B%E6%A9%9F-4g-%E7%B6%B2%E8%B7%AF%E4%B8%8A%E7%B6%B2%E9%80%9F%E5%BA%A6%E5%97%8E%EF%BC%9F
